This invention relates to a breather device for an internal combustion engine.
The breather device according to the prior art used in the internal combustion engine is so designed as to take a blowby gas into the lubricant separation chamber through the intake opening with or without the check valve, separate the oil entrained in the blowby gas in the separation chamber, and return the separated oil to the crank chamber through the return holes in the bottom of the separation chamber, as shown in U.S. Pat. Nos. 4,569,323, 4,603,673, 4,681,068 etc.
However, by the method simply with the return holes only formed in the bottom of the separation chamber, the oil collected in the bottom of the separation chamber will scatter, because the blowby gas flows at a high speed into the lubricant separation chamber not only from the check valve portion but also from the return holes when the pressure in the crank chamber is increasing (at the positive pressure).
Such a phenomenon will cause the amount of oil discharged into the intake air line to be increased, the air cleaner and the intake air passage to be fouled, blocked and dripped with oil, and eventually the consumption of lubricant to increase. Further, the fouling of the air cleaner will result in a loss of supply of combustion air, thus leading to a deterioration of engine performance.
In order to prevent the air cleaner from fouling, there is known the Japanese laid open utility model No. Sho61-2256, in which the breather device has return holes so slender as to decelerate the air speed flowing into the separation chamber when the pressure in the crank chamber is increasing, to prevent oil from scattering, but this invention also cannot fully return oil into the crank chamber through the slender return holes.
A breather arrangement for a cam case of an internal combustion engine is also disclosed in U.S. Pat. No. 4,651,704, which includes a hollow cam shaft disposed in the cam case, and formed a bore as a lubricant separation chamber extending axially therethrough, at least one blow-by gas inlet opening for admitting blow-by gas in the cam case, and at least one oil discharging opening for discharging oil which is deposited in the bore; and a breather pipe to one end of which the bore of the hollow cam shaft is communicated, the other end of the breather pipe communicating to an intake system of the engine.
In this case, however, there is a possibility of admitting the blow-by gas into the breather pipe before the entrained oil is separated from the blow-by gas by centrifugal forces due to rotation of the cam shaft.